reducing drone
 

is drone caused by the vibration in the pipes? If so would adding some hangers at various points help in reducing vibration (drone)? Love my FI but want to calm the drone down some while at 2K. I love the note when jumping on it and starting/idleing the car.

I have the 7AT w 12s, anyone have an AT with 18s? If so hows your drone?

Do you have just the exhaust or hfc too?

A lot of systems have a natural resonance at certain RPM's on certain cars. Not too much you can do at the exhaust level without major surgery, but sound deadening the car can reduce the annoyance..

Adding sound deadening to the interior of the car is the only real option. Be advised it is going to take a significant amount of quality mass-loaded volume to be able to block the drone and you are going to end up adding, at minimum, 50 lbs to the car.

Applying it to the hatch alone won't do much because there is no deadening in the rest of the car so it just finds other ways to get through... you'd have to do the whole floor and hatch to make a noticeable impact.

Since you have the 12" resonators you might want to consider swapping for the 18". You'd probably be able to resell your 12" so you might not take that much of a hit.

I have the 18" and the only real annoyance is with highway driving if I need to be applying throttle. Flat roads are fine, but throw some hills and mountains in there and you are constantly dealing with that noise. Everywhere else I think the sound levels are fine.

You're killing me, Steve!!!

The drone, I would guess, is caused my the lower volume of air going through the exhaust. Increase air flow -> increased tone/volume of exhaust. The resonators are there, I believe, to reduce that drone, at the cost of upper-RPM goodness. The 18" resonators won't be as loud and deep as non-resonated, but drone will be worse. You should be right in the middle with 12" resonators.

My belief is that in order to get your ideal tone at 4-6k RPM, you have to be ready for the 2k RPM "drone".

None of this is fact or professional opinion, btw. If you have any issues, I'll gladly take the exhaust off your hands!

Hmmm. I seem to remember Tony very clearly stating that the resonators were only there for sound control and that the only difference between non-res, 12, and 18, was the volume.

The treatment depends on if the drone you hear is structural or airborne noise related. If structural, adding damping at the attach points of the exhaust would help minimize the energy getting into the structure. If airborne then the mass addition to the interior panels is the way to go only after identifying which panels are the greatest contributors. If most of the airborne noise is vibrating your windows you are pretty much screwed unless you can change the modal characteristics of the window ("add a heavy tint layer"......joking).

Notice all the "ifs". Careful effort identifying the "source-path-reciever" will enable the least amount of weight addition.

You gained HP why throw some of that goodness away by adding unnecessary weight?

My Corvette had a big plastic tub sitting right over the Mufflers. After installing headers and HFC's I had an issue. It resonated like a Bass drum. On Vette's the drone RPM is 16-1800 RPM's which is easy to work around with the next lowest gear selection. Regardless, a liberal coat of Second Skin Damplifier helped quite a bit. Maybe 25-30 lbs worth. Some Z guys have done this...Check over in the Audio section.

http://images33.fotki.com/v1119/phot...MG_2161-vi.jpg

http://images33.fotki.com/v1120/phot...MG_2159-vi.jpg

is that how bad the drone is for the FI exhaust, i thought everybody was all saying that there wasn't drone, i guess you can't trust everybody's reviews on it

Yee-Haaawwww!! Let's have a bar-b-que!! Looks like you can throw the chicken right on top of that foil!

(sorry)

When I was shopping for CBEs, my intuition was that the FI droned but owners weren't admitting it. A few guys slowly began to say things like "it's a little loud at 2k rpm but you might not care." That was enough for me to realize the hype of waiting and then finally receiving their exhaust meant they couldn't bring themselves to say anything negative about it. I do love the way the FI exhaust sounds in the videos, but there's drone. Even Tony says in his video "very little drone, if any at all" which to mean translates into "some drone but I don't want to say no drone cus I'd be deceiving". Still loving my Stillen CBE.

I have been the most vocal about it and have caught a lot of flack for it from many of the FI guys. Oh well... just trying to help the community.

Anyways, Modshack, that's what I did... a coating of damplifier topped with Luxury Liner Pro in the hatch. It made a small difference but I'd need to do the entire car to be most effective. I did get rid of some hatch rattles, though, so that was nice. :)

Look at it this way - you're making those of us who went with Stillen feel better about it :rolleyes:

I wouldn't trust anyone's review here. Hate to say it, but more than a few here think mind numbing drone and alarm triggering noise levels are the Cat's meow..
I watched the Corvette guys cycle through 3, 4 or 5 different exhausts (at $1000 a crack) based on "Reviews" until they found one they liked. I suspect we'd have more of this here if Z owners had the Mod money the Vette guys do

My fear with Stillen, and potentially the future Berk CBE, is that it won't be loud enough. If I have to deal with a little drone to get the tone of the FI, so be it.

How aggressive is the stillen? From the look of the muffler design, I wouldn't guess it's too loud at all, just a little throatier than stock.

I'm looking hard at FI and Berk right now.

After researching and all, I have found that almost all aftermarket exhausts will have the 2K drone and that is the only time I am getting it, when around 60 mph in "D" mode at around 2k rpms. When with the wife who likes to talk while I drive its noticable but when its just me and Im usually on the gas I get that nice deep growl I like. And when Im driving at that one point it does drone I usually have the stereo up load and dont hear it. Just when the wife is with me that its a little loud. Now I willsay I love the tone of this exhaust better than any other one I heard on here so far and there are gains. Just wondering if I can cut down on the 2K drone some. Also I have the 7AT which might make a diff with the drone. So going to 18s will or wont help with this?

So Stillen doesnt drone any?

That's fine. I just make sure to be honest when giving feedback. I love the sound of my FI CBE and don't regret getting it. Yes, there is some drone at 2k but the benefit far outweighs the cost. I have heard the Stillen setup and some others and they all sound raspy to me... the only one with absolutely ZERO rasp is FI... it puts the others to shame, IMO.

If you like it, that's great. That's all that matters.

I can't count how many times I have said how much I like this exhaust, yet people continue to rag on me for talking about drone. It's ridiculous and plain childish!

We'd have to ask Tony about the difference the resonators would make.

I am the same way as you. My girlfriend has sensitive hearing so not just the drone, but the volume alone bothers her on any extended trips.

When I am by myself I am not bothered. It's there, but it's not a real bother. The ECU whine cuts through the drone and pierces my ears anyways. That's the only thing in the car noise-wise that bothers me. Actually it kills me.

Not that I can tell. It sounds better, but noticeably louder, at low RPMs.

So far no ECU noise for me that I can hear but I have slight hearing loss at the 6K freq anyway.

No drone from the Stillen..

:confused:

Was doing some research and read that side branch resonators seemed to help the drone by getting the freqs 180 degrees out of phase with each other that end up canceling each other. Is that why the Saclam exhaust looks the way it does? I was wondering if adding something like that would help reduce it but keep the same tone.

Still, I love the tone of the exhaust so I guees the wife just cant ride in it as much, cuz when Im alone in it Im hardly ever at the 2K range for my style of driving (FAST).

After reading more into their exhaust it seems that the Saclam has added side pipes to help with drone.

I think the Stillen CBE alone sounds good, but if you throw HFCs on it really sounds like crap. Some CBEs get very raspy when you add HFCs and the Stillen is one of those.

So if add a side pipe would reduce drone even 50% what size diameter and length would be required? Looking for all the math/science guys on this one.

I think that would just end up being an epic waste of money. I thought the Saclam exhaust had cutouts to bypass the muffler anyways... i know nothing about side tube resonators... if they exist... and if they even work.

I know the situation you are in, too. A little bit of it is guilt because you don't like that your significant other no longer likes riding in the Z with you because of the exhaust. When she's in the car with you, you feel bad because you know she's bothered.

But when you are alone, you enjoy it.

Instead of wasting money, just let time pass and you will get over it and it will get better. Don't let the guilt get to you.

Yeah, it sucks that my car gives my girlfriend headaches.... but have you heard how f'ing awesome it sounds? Priorities. :)

I agree and the wife isnt in it much but now Im just more curious about all this side branch stuff. Ive been googleing it alot and it seems the side branch pipes are a legit way of getting rid of low freq noise (its used in cars, buildings, plants, etc that have generators). I think the Saclam used what is called a trombone style side branch modified a tad. The thing you have to calculate is what freq is producing the drone and then calculate the right length of the side branch to get it to bounce back 180 degrees out of phase to cancel each other out. Sounds pretty interesting. And it would be easy to tap into existing exhaust if you get the right deminsions.

Curiousity has got my attention.

Does the Ark exhaust have the pipes you are talking about?

Yep looks like they do but also looks like it went into a deadend resonator too. That might be to reduce the length of the piping. I think the side pipe has to be the correct lambda length (which I guess is the length it takes a freq to travel) to achieve that 180 degree out of phase and maybe that wider pipe helped trick it to that. Im telling you this has me really curious now.


Actually the Ark and FI are very similar, Ark just has the side pipes.

I think it's a litte more complex than that... Typically those chambers are called Helmholtz resonators. They are used to dampen resonances
but usually used in intakes. There is one on the Z in the drivers side intake accordion. You'll see them on many cars in various shapes, tuned to cancel out natural frequencies. I think it would take some smart acoustical engineer to come up with something for the exhaust that would work on your system..

I was researching some more and saw this with one of my googles:

I’m a car-audio installer. An instructor at a training conference told me that clitoral resonance is 33 hertz, give or take, depending on the woman’s weight. This means that anything vibrating 33 times per second will cause the clitoris to resonate. Howard Stern made an example of this in Private Parts when he got a woman off by having her sit on a speaker, and just about any woman will respond to a bass note at that frequency if your subwoofer can play that low. Is there any truth to this? – J.B., Yuma Arizona

At 2K rpms 33 hertz is the drone freq:

So our girls should be jumping with pleasure when riding in our cars. Gonna have to get the wife to give it a try, maybe she will like the exhaust more then.

Hmmm, interesting. Did you have the Stillen with HFCs or just heard someone else's? Video or in person?

Most Stillen CBE owners on here have the HFCs as well. They seem to really like it, but again this could be owner-bias.

When I put the Stillen CBE on my car (No HFCs), the sound was noticeably louder and really a nice improvement. Having had it on the car for about 2-3 months now, I think I can go for another step up in loudness. There is ZERO drone with the Stillen CBE alone. I was going to add HFCs sometime in the next few months. However, I'm curious about this comment from M4A1. His review of the FI exhaust was an important part of my decision to go with the Stillen exhaust (and so far so good...I'm happy).

As for people giving M4A1 a hard time for saying the FI has some 2k drone...more and more people are admitting the same finding. Also, come on guys, we're above ragging on someone for sharing their opinion. Don't hate the player, hate the drone.

Video and in person.

But yeah... I have gotten a bad rap for that, even though I have expressly stated many times it's not that bad and I don't regret my choice one bit. Pisses me off! I just share my experience to the best of my ability and hope that it helps people make an informed decision.

Ok I would like to chime in on this. I have read through every reply here and would like to offer my input.

There are many factors to take in to account when designing a system.

-Sound
-Weight
-PERFORMANCE
-Aesthetics

Now me personally I do not feel that the drone at 2000-2400 RPM's is obtrusive. Again, this is me and sound is subjective. We are not in the business of putting a system out there just to put it out there, like some of our competitors who I will not name. If I felt the drone was overwhelming I would of made changes to compensate. I hear some comment on other systems and say they have no drone. Well, look at the design, some have suitcase mufflers which are horrible for performance and weigh a ton. Who wants to put an aftermarket system on their car that weighs 10-20 pounds over stock. Others have to compensate with giant silencers which divert the exhaust flow and again, affect performance and look like scuba tanks hanging off of your car.
To date we have sold 60 cat back exhaust systems and over 50 of them are installed. I can count on less than one hand how many people are either bothered or somewhat bothered by the drone. I have spoke to some of them on my own and they tell me that they would do it all over again knowing what they know now. I hear the same thing, there is some drone at 2000-2400ish but the sound is incredible.

"Is is so deep and smooth under acceleration and I just love it Tony".

-We are a minimum of 10 pounds lighter than stock.
-We picked up and average of over 20 RWH over stock.
-The exhaust looks aggressive yet classy.
-You will not find better customer service and I will stand behind that and my business until the end!!!
-To date: naturally aspirated we have higher gains over stock than any other 2.5" system on the market. And like I always say, put this system in a force inducted application, we will decimate any other 2.5" system in sound and performance.

The bottom line is, overall we feel that we have designed a system that brings the best qualities out of this wonderful car. In the end if the only major complaint is the drone that some feel they get, I will take it any day of the week.

If anyone has any questions, please do not hesitate to ask. I always have an open door policy...

Thank you, Tony

And that is the truth.

I know some people are very selective readers when they go through my posts regarding the FI exhaust, but I can't tell you how many times I have compared the sound to a Mustang Cobra mixed with a Ferrari F355. I absolutely rave about the sound. But I guess since I'm not afraid to talk about the drone that I experience some people jump on that and only that... but if they really read everything I have to say I always disclaim that 1) it's subjective, 2) it isn't that much of a bother for me..., and 3) it sounds f'in amazing.

For probably the 100th time... I don't regret buying the system one bit. This is without a doubt the best sound for this car... when all others fail to produce the low-mid range beefy sound and spit out a lot of rasp up top, Tony has come up with something that is deep and powerful down low and screams like a refined exotic up top. ABSOLUTELY ZERO RASP.

http://www.the370z.com/group-buys/11...l-exhaust.html

"Here's my 2 cents:

Essentially the second set of pipes are Helmholtz resonators, this is purely acoustic in nature and not necessarily performance related. The performance related aspects of this system can be attributed to the less restrictive flow path compared to the OEM system (including the x-pipe). The design "engineers" need to speak up to a level of explanation that does not give away their tricks.

I like this system, I think I'll purchase it but will not move until we see comparative dynos."

The side branches most likely are targeting a limited RPM range where flow conditions set up the "drone". The ~2k rpm condition (where drone occurs) is probably the targeted design point for the resonators. Higher RPMs mean a different flow so this becomes an off condition for the resonator design and the side pipes are there for looks.....but I kind of like them anyway :tup:

Done with the book...

I would want the customers to have it any other way. Our final production comes in Dec 15th. We have already set aside a day to bring detailed results with videos. Until then, if you have any questions regarding our systems please do not hesitate to ask.

Alex

Some interesting stuff here. For those still pondering which exhaust, let me say this, FIs exhaust IMO sounds the best overall and I love it 90% of the time. The 10% I dont like is the 2K drone and it may be worse for me due to being an AT, even Tony says its worse on an AT. Looks is a 10/10, love the look, better than any other so far. Performance is there, I usedmy Gtech prior to the exhaust and did a 0 60 in 5.1 secs. That took me about 6-8 tries to get that. Went out the other day and the roads were still damp and had debre on them from days of rain and in the 2 tries I did I got a 5.2 secs in "D" mode, which before I was getting 5.4 secs. And a 5.1 in paddle mode but I couldnt get a good grip due to road conditions. Even before in paddle mode I was getting 5.2s and even a 5.3, now I easlily got the 5.1. When the temp is around 70 degrees I will go back out and hope the road debre isnt as bad either and do a bunch of runs. I think I shaved .2 secs of my 0 60 time with this exhaust.

Now as an older guy who travels to my daugthers college alot to visit and the wife is with me, and having an AT that loves to put the rpms at 2K I would love to find a reasonable fix to this just for those times. I wouldnt mind an extra 2-4 pounds on the exhaust for some side resonators to help this.

Tony I still think you have a super product and I would still get it over the others again but maybe an option of side resonators for those that might want would be a nice touch.

Just my 2 cents.